A disk drive system typically consists of one or more magnetic recording disks and control mechanisms for storing data within approximately circular tracks on a disk. A disk is composed of a substrate and one or more layers deposited on the substrate. In most systems, an aluminum substrate is used. However, alternative substrate materials such as glass have various performance benefits such that it may be desirable to use a glass substrate.
To produce a disk substrate from a blank sheet of metal-based material such as aluminum or aluminum magnesium, the sheet may be stamped to generate a disk substrate having an inner diameter (ID) and an outer diameter (OD). After stamping the ID and OD, the disk-shaped substrate may be heat treated to remove stresses and then polished. The disk may then be coated with a polymer overcoat.
The trend in the design of magnetic hard disk drives is to increase the recording density of a disk drive system. Recording density is a measure of the amount of data that may be stored in a given area of disk. One method for increasing recording densities is to pattern the surface of the disk to form discrete tracks, referred to as discrete track recording (DTR). DTR disks typically have a series of concentric raised zones (a.k.a., lands, elevations, etc.) storing data and recessed zones (a.k.a., troughs, valleys, grooves, etc.) that may store servo information. The recessed zones separate the raised zones to inhibit or prevent the unintended storage of data in the raised zones.
One method of producing DTR magnetic recoding disks is through the use of a pre-embossed rigid forming tool (a.k.a., stamper, embosser, etc.). An inverse of the surface pattern is generated on the stamper, which is directly imprinted on the surface(s) of a disk substrate. Thin film magnetic recording layers are then sputtered over the patterned surface of the substrate to produce the DTR media having a continuous magnetic layer extending over both the raised zones and the recessed zones. To imprint tracks on a data storage disk substrate, an imprinting template may be attached to a flexible support, whose curvature can be altered by applying hydrostatic pressure. By suitably varying the pressure, the imprinting surface can be brought into contact with the disk substrate.
An imprinted disk may not be viable if the imprinting surface is not concentrically aligned with the disk substrate. Imprinted tracks that have excessive offset from a centerline of the disk substrate may not operate properly when read by a disk drive head. This requirement is particularly important in disks used in hard disk drives in which tracks may need to be imprinted on both sides. As such, imprinting a disk requires an alignment step, in which a centerline of the disk is aligned with a centerline of the imprinting surface, before the disk substrate is actually imprinted.
Current alignment methods typically require the use of high precision actuators or robotics. For example, the high precision actuators would first determine a centerline for the disk substrate and align it with a centerline of the imprinting surface. The use of such high precision actuators and robotics are expensive, with high maintenance costs, inconsistent accuracy and reliability, and slow cycle times. The high precision actuators and robotics are also significant pieces of machinery, requiring large amounts of floor space.